Add function to load Qt API from environment, closes #69

qdarkstyle/__init__.py

@@ -30,18 +30,124 @@ with the correct rc file.
 """
 import logging
 import platform
+import os
 
 
-__version__ = "2.3.1"
+__version__ = "2.4"
+
+PYQTGRAPH_QT_LIB_VALUES = ['PyQt', 'PyQt5', 'PySide', 'PySide2']
+QT_API_VALUES = ['pyqt', 'pyqt5', 'pyside', 'pyside2']
 
 
 def _logger():
     return logging.getLogger('qdarkstyle')
 
 
+def _qt_wrapper_import(qt_api):
+    """
+    Check if Qt API defined can be imported.
+
+    :param qt_api: Qt API string to test import
+
+    :return load function fot given qt_api, otherwise empty string
+
+    """
+    qt_wrapper = ''
+    loader = ""
+
+    try:
+        if qt_api == 'PyQt' or qt_api == 'pyqt':
+            import PyQt4
+            qt_wrapper = 'PyQt4'
+            loader = load_stylesheet_pyqt()
+        elif qt_api == 'PyQt5' or qt_api == 'pyqt5':
+            import PyQt5
+            qt_wrapper = 'PyQt5'
+            loader = load_stylesheet_pyqt5()
+        elif qt_api == 'PySide' or qt_api == 'pyside':
+            import PySide
+            qt_wrapper = 'PySide'
+            loader = load_stylesheet_pyside()
+        elif qt_api == 'PySide2' or qt_api == 'pyside2':
+            import PySide2
+            qt_wrapper = 'PySide2'
+            loader = load_stylesheet_pyside2()
+    except ImportError as err:
+        _logger().error("Impossible import Qt wrapper. " + str(err))
+    else:
+        _logger().info("Using Qt wrapper = %s " % qt_wrapper)
+    finally:
+        return loader
+
+
+def load_stylesheet_from_environment(is_pyqtgraph=False):
+    """
+    Load the stylesheet from QT_API (or PYQTGRAPH_QT_LIB) environment variable.
+
+    :param is_pyqtgraph: True if it is to be set using PYQTGRAPH_QT_LIB
+
+    :raise KeyError: if QT_API/PYQTGRAPH_QT_LIB does not exist
+
+    :return the stylesheet string
+    """
+    qt_api = ''
+    pyqtgraph_qt_lib = ''
+
+    loader = ""
+
+    # Get values from QT_API
+    try:
+        qt_api = os.environ['QT_API']
+    except KeyError as err:
+        # Log this error just if using QT_API
+        if not is_pyqtgraph:
+            _logger().error("QT_API does not exist, do os.environ['QT_API']= "
+                            "and choose one option from %s" % QT_API_VALUES)
+    else:
+        if not is_pyqtgraph:
+            if qt_api in QT_API_VALUES:
+                _logger().info("Found QT_API='%s'" % qt_api)
+                loader = _qt_wrapper_import(qt_api)
+            else:
+                # Raise this error because the function need this key/value
+                raise KeyError("QT_API=%s is unknown, please use a value "
+                               "from %s" % (qt_api, QT_API_VALUES))
+
+    # Get values from PYQTGRAPH_QT_LIB
+    try:
+        pyqtgraph_qt_lib = os.environ['PYQTGRAPH_QT_LIB']
+    except KeyError as err:
+        # Log this error just if using PYQTGRAPH_QT_LIB
+        if is_pyqtgraph:
+            _logger().error("PYQTGRAP_QT_API does not exist, do "
+                            "os.environ['PYQTGRAPH_QT_LIB']= "
+                            "and choose one option from %s" %
+                            PYQTGRAPH_QT_LIB_VALUES)
+    else:
+        if is_pyqtgraph:
+            if pyqtgraph_qt_lib in PYQTGRAPH_QT_LIB_VALUES:
+                _logger().info("Found PYQTGRAPH_QT_LIB='%s'" % pyqtgraph_qt_lib)
+                loader = _qt_wrapper_import(pyqtgraph_qt_lib)
+            else:
+                # Raise this error because the function need this key/value
+                raise KeyError("PYQTGRAPH_QT_LIB=%s is unknown, please use a "
+                               "value from %s" % (pyqtgraph_qt_lib,
+                                                  PYQTGRAPH_QT_LIB_VALUES))
+
+    # Just a warning if both are set but differs each other
+    if qt_api and pyqtgraph_qt_lib:
+        if qt_api != pyqtgraph_qt_lib:
+            _logger().warning("Both QT_API=%s and PYQTGRAPH_QT_LIB=%s are set, "
+                              "but with different values, this could cause "
+                              "some issues if using them in the same project!"
+                              % (qt_api, pyqtgraph_qt_lib))
+
+    return loader
+
+
 def load_stylesheet(pyside=True):
     """
-    Loads the stylesheet. Takes care of importing the rc module.
+    Load the stylesheet. Takes care of importing the rc module.
 
     :param pyside: True to load the pyside rc file, False to load the PyQt rc file
 
@@ -81,9 +187,36 @@ def load_stylesheet(pyside=True):
         return stylesheet
 
 
+def load_stylesheet_pyside():
+    """
+    Load the stylesheet for use in a pyside application.
+
+    :return the stylesheet string
+    """
+    return load_stylesheet(pyside=True)
+
+
+def load_stylesheet_pyside2():
+    """
+    Load the stylesheet for use in a pyside2 application.
+
+    :raise NotImplementedError: Because it is not supported yet
+    """
+    raise NotImplementedError("PySide 2 is not supported yet.")
+
+
+def load_stylesheet_pyqt():
+    """
+    Load the stylesheet for use in a pyqt4 application.
+
+    :return the stylesheet string
+    """
+    return load_stylesheet(pyside=False)
+
+
 def load_stylesheet_pyqt5():
     """
-    Loads the stylesheet for use in a pyqt5 application.
+    Load the stylesheet for use in a pyqt5 application.
 
     :param pyside: True to load the pyside rc file, False to load the PyQt rc file